# install keepalived
yum install -y keepalived

# config keepalived for rotating & high availability virtual ip
cat > /etc/keepalived/keepalived.cfg << "EOF"
vrrp_script chk_haproxy {
  script "killall -0 haproxy" # health check script, will force master election when error code is yielded
  interval 2
  weight 5
}

vrrp_instance VI_1 {
  interface eth0
  state MASTER # or BACKUP for backup instances
  virtual_router_id 202 # must be synchronized across instances
  priority 101 # must vary across instances, highest priority instance is master
               # must ensure that (priority + health check weight) of lowest priority instance
               # be high enough to outweight highest priority amongst instances
  advert_int 1

  unicast_src_ip <node1> # ip of the instance
  unicast_peer {
    <node2> # ip of other instances, add more ip as necessary
  }

  // must be the same for all instances
  authentication {
    auth_type PASS
    auth_pass password
  }

  # virtual ip to bind to master instance
  virtual_ipaddress {
    <virtual ip>
  }

  # call check script defined above
  track_script {
    chk_haproxy
  }
}
EOF

# restart keepalived
systemctl restart keepalived